Monitoring of blood pressure by caregivers has become a well-established bio-monitoring tool. Knowledge of a patient's blood pressure is often essential to properly assess the patient's medical condition. Hypertension, hypotension, and shock are some examples of conditions monitored via blood pressure. Frequently, a sphygmomanometer (an instrument, often attached to an inflatable air-bladder cuff and used with a stethoscope, for measuring blood pressure in an artery) is used for such monitoring.
Continuous monitoring of the blood pressure enables medical personnel to immediately detect changes in the cardiovascular system indicating stress, and to respond rapidly with the appropriate action. While a sphygmomanometer is effective, continuous use of a sphygmomanometer is inconvenient. Accordingly, various approaches for continuous monitoring of blood pressure have been developed. One common approach involves inserting a needle into the artery or vein of a patient and exposing a catheter to the fluid pressure in the artery or vein. A sterile solution fills the catheter and the pressure of the cardiovascular system at that point in the body is transmitted through the sterile solution to a fluid pressure sensing device connected to the catheter outside the patient's body. A pressure-sensing device such as a pressure transducer is then used to produce an electric signal proportional to the fluid pressure of the blood at the open end of the catheter. While this type of system is useful when an individual is substantially immobilized, it is not useful for patients who are not confined to a bed.
One approach that overcomes some of the limitations of the above systems is the use of an implantable pressure monitor. U.S. Patent Publication Number 2004/0193058 describes an implantable pressure monitor. While the device in the '058 publication measures the blood pressure of an individual, the '058 device does not provide information as to the context of the particular blood pressure reading. For example, while a given blood pressure may be acceptable during and shortly after heavy exercise, that same blood pressure while an individual has been at rest for a period of time may indicate a problem in the individual.
Therefore, an improved implantable blood pressure sensor is needed. It would be advantageous if the blood pressure sensor provided insight as to the context of a particular blood pressure reading. A system which did not require external power sources to operate would be further beneficial.